The present invention relates to a device, fitted onto a carriage drafted along a track, adapted to increase the requirement of mechanical energy to the drafting system in order to use such increased energy to transform it into electric energy required to actuate various uses.
The equipment object of the present invention mainly applies to sorting machines of the “Cross belt” type.
These machines can exhibit different layouts (linear, carousel-like, L-shaped, etc.) and they consist of a train of carriages moving along a sorting path, from item input stations to devices for collecting sorted items. See, for example, U.S. Pat. Nos. 5,803,230, No. 6,209,703 and No. 6,253,904, the disclosures of which are incorporated herein by reference.
The term “Cross Belt” indicates that the sorting unit with which the carriage is equipped is a small conveyor belt capable of moving independently, by an electric motor, in the two directions orthogonal to the running direction of the sorting machine.
Such a sorting machine is therefore usually activated during the item loading step to house the same items onboard, and in the unloading step, in one or both directions, to direct the items to the appropriate destination. The energy required to actuate the conveyor belt is provided by an electric motor onboard of each carriage. The present invention involves a device disposed on each carriage adapted to draw mechanical energy from the carriage movement and transfer it onboard of the same carriage, where it is transformed into electric energy to provide for the actuation of conveyor belts onboard the same carriage.
Several methods and devices are known in the prior art, adapted to transfer the electric energy onboard of the train of carriages, required to operate the motors drafting the conveyor belts.
A method for transferring electric energy onboard of the train of carriages consists in a system of busways arranged along the machine and powered by several feeders (typically 70 V 100 A). Onboard of some carriages there are sliding contacts that allow drawing the electric energy that will be transferred to the other carriages by a wiring arranged along the entire train of carriages. Such solution is technically valid and widely tested, but it exhibits some technical disadvantages. In the first place, it is expensive because the busways, which are made of copper, must be arranged perfectly parallel to the machine. Moreover, if they are loose, they vibrate and cause the breaking of the sliding contacts. In turn, also sliding contacts are expensive since they consist of pantographs that are difficult to implement; moreover, contacts are subject to wear and to accidental breakage. Finally, to limit wear, the busways must be oversized to stand high-energy requirements in case of concurrent actuation of several carriages.
Another method consists in the inductive transmission of electric energy. A pair of wires, forming a maxi-turn along the entire machine, forms a closed circuit in which a generator transmits an alternate current of 50-100 A at an approximate frequency of 28 kHz. The current flowing into the two wires generates a concentric magnetic field around the two wires. The E core of transformers installed on the carriages faces the two wires, thereby closing the magnetic circuit. An alternate current is induced through the turns wound on such core, and it can be straightened and used for powering the onboard motor. Such solution is conceptually simple but it exhibits two serious disadvantages; in the first place, high frequencies induce parasitic currents in metal items placed nearby. Therefore, besides the serious attenuation problems, it is necessary to set up suitable protections to prevent potentially hazardous situations for maintenance personnel. In addition, efficiency in the transmission of power peaks is so low that it requires onboard accumulators to deliver strong current peaks, when required.
Another method consists in using the mechanical energy of the carriage drafting system, transferring it onboard each carriage by a pressure wheel fitted on each of said carriages, and converting it into electric energy by a generator actuated by said wheel.
On the average, a machine may require about 3 KW of electric power for loading and sorting, but situations may occur where even 20 KW are required due to the concurrent unloading of several items, by statistic combination. Such disadvantage is solved by equipping each carriage with a battery: the generator, constantly working during the machine movement, charges the battery which therefore, during the travel of the machine, accumulates the energy that will discharge in the few seconds required to load or unload the carriage. In this way, even with a small power generator, it is possible to have the electric power required for loading and unloading operations.
However, such a solution is very complex since, besides the generator, an onboard battery is required and batteries are expensive, polluting, heavy and have a short operating life.
Batteries must be properly protected since they may be dangerous for operators close to the sorting machine, in the event of mechanical jamming caused by the transported items.
Moreover, there is one of such units for each carriage and in addition to the generator and battery, the units also include a controller, which considerably increases costs.
Such disadvantages are overcome by the application of a method and relevant device, which is the object of a commonly owned, concurrently filed U.S. patent application Serial No. 10/410,209 (corresponding to Italian Application Serial No. MI2002A 000785 filed Apr. 12, 2002), to which reference should be made for further details, according to which energy is not stored in the batteries as electric energy, but rather in the moving train of carriages, that is, using the high capacity of storage of mechanical energy of the same machine through its kinetic energy.
Since with the application of such method the instantaneous powers needed to transfer items onboard of the carriages can be very high, the drafted wheels must be strongly compressed against the track to prevent frictional sliding of the wheels, but this highly stresses the mechanical members.
Moreover, the prior art that provides for the use of a toothed wheel engaging a rack is expensive and causes excessive noise.